# Around the Rainbow (DD-651) > A rainbow isn't an object in a fixed place. It's a pattern of light that appears when sunlight enters falling drops, bends (refracts) going in, reflects once off the back of each drop, and bends again on the way out. Different colors leave at slightly different angles, so the drops that send light to your eye all sit about 40 to 42° from the antisolar point. That's the point directly opposite the sun, which is always where the shadow of your head falls. Every point on a circle at that angle around your shadow sends rainbow light to you, so the primary rainbow is a ring, red on the outside and violet on the inside. From the ground, the antisolar point is below the horizon whenever the sun is up. You see only the part of the circle above the ground, and only if there are raindrops there. When the sun is right on the horizon you get a half circle, and the higher the sun, the smaller the arc. Once the sun is higher than about 42°, no primary bow appears at ground level. From an airplane, a mountain or a tall building, drops can lie below you too, so you can sometimes see the whole ring. A glory is a different effect: smaller, tighter colored rings around the shadow of an aircraft on cloud. The footage shows a bright rainbow arcing down past the horizon toward the water below, filmed from high above a waterfront. - Department: Science (also Nature) - First published: 2025-09-19 - Last updated: 2025-09-19 - Permalink: https://detailenjoyer.com/case/around-the-rainbow/ - Author: Marcus Easterling (DetailEnjoyer), The Detail Department ## Quick facts - **DD-651-F01**: A primary rainbow forms about 42° from the antisolar point. _(Write-up · Exhibit B (A 42° ring))_ - **DD-651-F02**: From aircraft, rainbows can appear as full circles. _(Write-up · Exhibit E (The whole ring))_ ## Write-up Rainbows are secretly circles. From high up, the horizon stops cutting the ring in half. 1. **Refract, reflect, refract**: Sunlight bends entering a drop, reflects off the back, and bends again on the way out. 2. **A 42° ring**: The primary bow forms about 40 to 42° from the point directly opposite the sun. 3. **Why we see arcs**: From the ground, that circle's center is below the horizon, so only part of it shows. 4. **Higher sun, smaller arc**: When the sun is higher than about 42°, no primary bow is visible from the ground. 5. **The whole ring**: From aircraft or other high places, drops below you can complete the circle. ## Related case files - [Branched Flow (DD-739)](https://detailenjoyer.com/case/branched-flow/): More patterns made by light - [UV Face (DD-654)](https://detailenjoyer.com/case/uv-face/): Another case about how light and eyes work ## Reel vs. record - **Note**: 'The horizon blocking the bottom half': you only see half the circle when the sun is on the horizon. The higher the sun, the less of the circle shows, and when the sun is above about 42°, none of it does. - **Note**: 'They are full circles': the circle is a set of directions centered on the antisolar point. You only see the parts where there are raindrops lit by the sun along those directions. - **Note**: 'From high vantage points... the entire circle': this needs sunlit drops below you as well, and the sun behind you. Full rings are most often seen from aircraft, or from high above spray or rain. - **Note**: 'Refracted and reflected light': correct. The primary bow involves two refractions and one internal reflection in each drop, which is why red is on the outside. - **Not the same as a glory**: the small colored rings sometimes seen around a plane's shadow on cloud are a glory, a different optical effect from a full-circle rainbow. ## Video: Around the Rainbow: Rainbows Are Secretly Circles - Duration: 18.5 s · Published: 2025-09-19 - File: https://detailenjoyer.com/assets/videos/DOyz2iREZKa.mp4 ### Transcript DID YOU KNOW? Rainbows are often seen as arcs from the ground, but in reality they are full circles of refracted and reflected light with the horizon blocking the bottom half from view. From high vantage points observers can sometimes see the entire circle because the Earth's surface no longer cuts off the view, revealing the rainbow's true geometry. NOW YOU KNOW! ## Questions & answers **Q: About how far from the antisolar point does the primary rainbow form?** A: About 40 to 42°. _(Source: Write-up · Exhibit A (Refract, reflect, refract) · HyperPhysics (Georgia State University): Primary and secondary rainbows; National Geographic Education: Rainbow)_ **Q: Where is the antisolar point?** A: Where the shadow of your head falls. _(Source: Write-up · Exhibit A (Refract, reflect, refract) · HyperPhysics (Georgia State University): Primary and secondary rainbows; National Geographic Education: Rainbow)_ **Q: What color is on the outside of a primary rainbow?** A: Violet is on the inside. _(Source: Write-up · Exhibit A (Refract, reflect, refract) · HyperPhysics (Georgia State University): Primary and secondary rainbows; National Geographic Education: Rainbow)_ **Q: What happens to the bow when the sun is higher than about 42°?** A: The whole circle drops below the horizon. _(Source: Write-up · Exhibit A (Refract, reflect, refract) · HyperPhysics (Georgia State University): Primary and secondary rainbows; National Geographic Education: Rainbow)_ **Q: Where are full-circle rainbows most often seen?** A: Drops below you complete the ring. _(Source: Write-up · Exhibit B (A 42° ring) · WMO International Cloud Atlas: Primary rainbow; HyperPhysics (Georgia State University): Primary and secondary rainbows)_ ## Sources - [WMO International Cloud Atlas: Primary rainbow](https://cloudatlas.wmo.int/en/primary-rainbow.html) - [HyperPhysics (Georgia State University): Primary and secondary rainbows](https://www.hyperphysics.gsu.edu/hbase/atmos/rbowpri.html) - [BBC Science Focus: Why are rainbows circular when viewed from an aeroplane?](https://www.sciencefocus.com/science/why-are-rainbows-circular-when-viewed-from-an-aeroplane) - [National Geographic Education: Rainbow](https://education.nationalgeographic.org/resource/rainbow/) ## Cite this case file Easterling, Marcus. "Around the Rainbow." The Detail Department (DetailEnjoyer), case file DD-651, last updated Sep 19, 2025. https://detailenjoyer.com/case/around-the-rainbow/